The field relates generally to machining and other fabrication and manufacturing processes, and more specifically, to methods and apparatus for reducing wear of surfaces in contact with relative motion with respect to one another, including, for example, sliding, rolling, and other forms of motion.
Many processes are known where friction from a first metal device engaging a second metal device produces heat, wear, deformation, and surface blemishes. Sometimes, the two devices may be different metals, one of the devices may not be a metal, or neither of the devices may be metal, such as ceramic. One simple example is the drilling of holes into a component using a bit. In many of these applications, the wear resulting from the sliding engagement between the two devices eventually results in reduced quality, increased heat generation and a corresponding reduction in process speed or reduced energy efficiency. Other detrimental results from the above described sliding engagement between two surfaces are also known. Types of wear include erosion, cavitation, rolling, sliding and rolling, and impact (large body, small particle, and liquid). Types of contact between surfaces can include sliding abrasion (“two body”), rolling abrasion (“three body”) and scratching.
Reducing wear in such applications is desired since it allows a tool or a die to be used longer simply because it lasts longer. In physical terms, reducing wear translates into reducing the rate at which material from one of the devices is removed from its acting surface. In one practical example, reducing wear allows a drill bit to drill more holes before it needs to be replaced. The drill bit can be used longer because the surface quality, including for example a smoothness associated with the surface, is less adversely affected.
Current implementations within such processes do not necessarily reduce wear. Instead, such implementations attempt to reduce friction. Solutions for reducing friction include the adding of lubricants, such as oils, greases, and solid lubricants, for example, molybdenum disulfide (MoS2), to processes; and dry lubricants such as coatings and powders. Other solutions include custom coatings applied to the surface where engagement is expected to occur.
Various custom coatings can be used to protect surfaces, such as coating the cutting surfaces of drill bits. However, once the drill bit is worn out (in some applications this can occur in as few as three holes, at $75/bit, for some composite material drilling processes), it must be reground. Regrinding removes the coating so the bit must also go through the coating processes again before it can once again be utilized in the process.
While the accumulation and agglomeration of wear particles at the sliding interface and their adverse effects on friction and wear are known, the means for breaking down wear agglomerates has not been well considered. One beneficial method is to develop a method or system to reduce particle size that can accumulate between sliding surfaces, especially in applications with substantial forces between the surfaces. Particle size reduction can result in greater direct contact between the surfaces. Such a method and system would improve efficiency and cost effectiveness of many industrial applications such as drilling and grinding.